Underwater versus conventional EMR for colorectal polyps: systematic review and meta-analysis

Underwater EMR (UEMR) has emerged as an attractive alternative to conventional EMR (CEMR) for the resection of colorectal polyps. The purpose of this systematic review and meta-analysis was to compare UEMR and CEMR for the resection of colorectal polyps with respect to efficacy and safety.

A literature search was performed across multiple databases, including MEDLINE/PubMed, The Cochrane Library, CINAHL, Google Scholar, and Scopus, for studies that were published until May 2020. Only studies that compared the resection of colorectal polyps using UEMR with CEMR were included. Outcomes examined included rates of en bloc resection, recurrence, postprocedure bleeding, perforation, and resection time.

Seven studies totaling 1237 polyps were included: 614 polyps were resected with UEMR and 623 polyps with CEMR. UEMR was associated with a significant increase in the rate of overall en bloc resection (odds ratio [OR], 1.84; 95% confidence interval [CI], 1.42-2.39; P < .001; I² = 38%), with subgroup analysis showing a significant increase in the rates of en bloc resection in polyps ≥20 mm (OR, 1.51; 95% CI, 1.06-2.14; P = .02; I² = 44%) but not in polyps <20 mm (OR, 1.07; 95% CI, .65-1.76; P = .80; I² = 27%), and with a significant reduction in the rate of recurrence (OR, .30; 95% CI, .16-.57; P = .0002; I² = 0%), again driven by improvements in polyps ≥20 mm. There was no significant difference in postprocedure bleeding (OR, 1.11; 95% CI, .57-2.17; P = .76; I² = 0%) or perforation (OR, .72; 95% CI, .19-2.83; P = .64; I² = 0%).

The results of this systematic review and meta-analysis demonstrate that UEMR is a safe and efficacious alternative to CEMR. With appropriate training, UEMR may be strongly considered as a first-line option for resection of colorectal polyps.